Space History for April 21

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1965Died, Edward V. Appleton, English physicist (ionosphere, sunspots, Nobel Prize 1947 "for his investigations of the physics of the upper atmosphere especially for the discovery of the so-called Appleton layer")ref:nobelprize.org

1967Died, Andre L. Danjon, French astronomer (Danjon Scale, color brightness of the Moon during a Lunar eclipse due to Earth's atmospheric conditions)ref:en.wikipedia.org

1972 02:23:35 GMTNASA's Apollo 16 Lunar Module "Orion" landed on the Moon during the fifth manned landing mission, carrying Commander John W. Young and LM pilot Charles M. Duke Jr., the ninth and tenth men to walk on the Moon.
Apollo 16 Lunar Module, NASA photo taken by an astronaut on the Moon

Apollo 16 (AS 511) consisted of the Command and Service Module (CSM) "Casper" and the Lunar Module (LM) "Orion." The launch on 16 April 1972 was postponed from the originally scheduled 17 March date because of a docking ring jettison malfunction. It was the fifth mission in which humans walked on the Lunar surface and returned to Earth. On 21 April 1972 two astronauts (Apollo 16 Commander John W. Young and LM pilot Charles M. Duke, Jr.) landed in the Descartes region of the Moon in the Lunar Module (LM) while the Command and Service Module (CSM) (with CM pilot Thomas K. Mattingly, II) continued in Lunar orbit. During their stay on the Moon, the astronauts set up scientific experiments, took photographs, and collected Lunar samples. The LM took off from the Moon on 24 April and the astronauts returned to Earth on 27 April.

The primary mission goals of inspecting, surveying, and sampling materials in the Descartes region, emplacement and activation of surface experiments, conducting inflight experiments and photographic tasks from Lunar orbit, engineering evaluation of spacecraft and equipment, and performance of zero-gravity experiments were achieved despite the mission being shortened by one day. Young, 41, was a Navy Captain who had flown on three previous spaceflights (Gemini 3, Gemini 10, and Apollo 10; he later flew on STS-1 and STS-9), Mattingly, 36, was a Navy Lt. Commander on his first spaceflight (he later flew STS-4 and STS-51C), and Duke, 36, was an Air Force Lt. Colonel also on his first spaceflight.

Apollo 16 was launched at 17:54:00 (12:54:00 p.m. EST) on Saturn V SA-511 from Pad 39A at the Kennedy Space Center, Florida. The spacecraft entered Earth parking orbit at 18:05:56 UT and translunar injection took place at 20:27:37 UT. The CSM and S-IVB stage separated at 20:58:59 UT and CSM-LM docking was achieved at 21:15:53 UT. The S-IVB stage was released into a Lunar impact trajectory, but due to an earlier problem with the auxiliary propulsion system (APS) helium regulators, which resulted in continuous venting and loss of helium, the second APS burn could not be made. Tracking of the S-IVB was lost on 17 April at 21:03 UT due to a transponder failure. (The S-IVB stage impacted the Moon on 19 April at 21:02:04 UT at 1.3 N, 23.8 W with a velocity of 2.5 to 2.6 km/s at a 79 degree angle from the horizontal, as estimated from the Apollo 12, 14 and 15 seismic station data.) A mid-course correction was performed at 00:33:01 UT on 18 April. During translunar coast a CSM navigation problem was discovered in which a false indication would cause loss of inertial reference, this was solved by a real-time change in the computer program. The SIM door was jettisoned on 19 April at 15:57:00 UT and Lunar orbit insertion took place at 20:22:28 UT. Two revolutions later, the orbit was lowered to one with a perilune of 20 km.

At 15:24 UT on 20 April, Young and Duke entered the LM. The LM separated from the CSM at 18:08:00 UT, but the LM descent was delayed almost 6 hours due to a malfunction in the yaw gimbal servo loop on the CSM which caused oscillations in the service propulsion system (SPS). Engineers determined that the problem would not seriously affect CSM steering and the mission was allowed to continue with the LM descent. The LM landed at 02:23:35 UT on 21 April in the Descartes highland region just north of the crater Dolland at 9.0 S, 15.5 E. Young and Duke made three moonwalk EVAs totaling 20 hours, 14 minutes. During this time they covered 27 km using the Lunar Roving Vehicle, collected 94.7 kg of rock and soil samples, took photographs, and set up the ALSEP and other scientific experiments. Other experiments were also performed from orbit in the CSM during this time.

The LM lifted off from the Moon at 01:25:48 UT on 24 April after 71 hours, 2 minutes on the Lunar surface. After the LM docked with the CSM at 03:35:18 UT the Lunar samples and other equipment were transferred from the LM and the LM was jettisoned at 20:54:12 UT on 24 April. The LM began tumbling, apparently due to an open circuit breaker in the guidance and navigation system. As a result the planned deorbit and Lunar impact could not be attempted. The LM remained in Lunar orbit with an estimated lifetime of one year. The instrument boom which carried the orbital mass spectrometer would not retract and was jettisoned. Because of earlier problems with the SPS yaw gimbal servo loop the mission was shortened by one day. The orbital shaping maneuver was cancelled, and the subsatellite was spring-launched at 21:56:09 UT into an elliptical orbit with a lifetime of one month, rather than the planned one-year orbit. Transearth injection began at 02:15:33 UT on 25 April. On 25 April at 20:43 UT Mattingly began a cislunar EVA to retrieve camera film from the SIM bay and inspect instruments, two trips taking a total of 1 hour, 24 minutes. The CM separated from the SM on 27 April at 19:16:33 UT. Apollo 16 splashed down in the Pacific Ocean on 27 April 1972 at 19:45:05 UT (2:45:05 p.m. EST) after a mission elapsed timeof 265 hours, 51 minutes, 5 seconds. The splashdown point was 0 deg 43 min S, 156 deg 13 min W, 215 miles southeast of Christmas Island and 5 km (3 mi) from the recovery ship USS Ticonderoga.

The Apollo Lunar Surface Experiments Package (ALSEP), which contained scientific experiments that were deployed and left on the Lunar surface, operated until it was commanded to shut down on 30 September 1977.

The Apollo 16 Command Module "Casper" is on display at the Alabama Space and Rocket Center in Huntsville, Alabama.

2001 08:59:00 CDT (GMT -5:00:00)NASA's STS 100 (Endeavor) docked at the International Space Station on a mission to deliver the Canadian robotic arm.

STS 100 was launched 19 April 2001. Endeavour and its crew remained on orbit almost 12 days, eight of which were spent in joint operations with the International Space Station crew. Endeavour's crew delivered and installed a new robotic arm and helped to transfer equipment and supplies between vehicles.

Mission Specialists Chris Hadfield of the Canadian Space Agency and Scott Parazynski of NASA performed two space walks to install the new 17.6 meter (57.7 foot) robotic arm onto the International Space Station. Canadarm2, a beefier second-generation version of the shuttle's robot arm, is essential to the continued assembly of the space station as the outpost grows beyond the reach of the shuttle's arm.

STS 100 was the first of three space shuttle missions to carry pieces of the Space Station Mobile Servicer System, or SSMSS to the station. It delivered the long, hinged arm known as the Remote Manipulator System. Subsequent missions delivered the Mobile Base System, a work platform that moves along rails covering the length of the space station, and the Special Purpose Dexterous Manipulator, or Canada Hand.

The International Space Station's three Command and Control Computers began to exhibit problems during Endeavour's visit. Communications between the station and the ground were rerouted through Endeavour as flight controllers worked to solve the problem, and mission managers approved an extended stay for the shuttle if the computers were not recovered quickly.

After flight controllers determined that the hard drive on one Command and Control Computer had failed, space station Flight Engineer Susan Helms swapped it with another onboard computer. After reloading the software, all three computers booted up normally. Endeavour brought the failed computer back to Earth for more testing.

STS 100 ended 1 May 2001 when Endeavour landed at Edwards Air Force Base, California, after being waved off from landings at Kennedy Space Center because of the inclement weather in Florida.

International Space Station Expedition 9 commander Gennady Padalka and NASA science officer Michael Fincke lived aboard the station from 21 April 2004 through 23 October 2004. They returned to Earth in their Soyuz TMA-4 spacecraft which landed at 8:36 PM EDT (0036 GMT). Russian Space Forces cosmonaut Yuri Shargin, an ISS visitor, also rode the in the Soyuz return flight.

Padalka and Fincke returned home after an eventful 188-day tour in space that began on with their launch on 18 April 2004. They made some unexpected repairs and conducted four spacewalks, including one of the shortest on record and another that marked the first use of Russian spacesuits for a US segment operation.ref:spaceflight.nasa.gov